The overall goal of the Transfusion Medicine/Hemostasis Clinical Research Network is to efficiently conduct multi-center clinical studies (primarily randomized clinical trials), to evaluate treatments and management strategies for children and adults with hemostatic disorders. The New England ResearchInstitutes (NERI) proposes to support the Network as Data Coordinating Center (DCC). This proposal describes DCC methods and presents an innovative randomized clinical trial design for the treatment of thrombotic thromocytopenic purpura (TTP). The DCC has the following aims: 1) to collaborate in the selection, design, conduct, analysis and reporting of clinical studies and trials; 2) to establish a mechanism for randomization and monitoring of patient recruitment from both Network and non-Network centers; 3) to develop and maintain a data management system for each Network study; 4) to compile, edit, analyze and report study data; 5) to institute quality control procedures including training study personnel and conducting site visits; 6) to identify central laboratories and repositories, and to develop a system for tracking laboratory specimens and results; 7) to achieve cost and time efficiencies for study start-up by maintaining a standard library of data collection modules; 8) to develop and administer a mechanism for patient recruitment and retention from out-of-network centers; and 9) to coordinate the activities of the Steering Committee, Protocol Review Committee, Data and Safety Monitoring Board with communication and meeting support. The NERI team of investigators offers considerable experience in coordinating complex multi-center studies with expertise in administrative and biostatistical support, data management, quality control procedures and quality of life measurement. Clinical expertise in the fields of hemostasis and transfusion medicine is provided locally by Dr. Kruskall of Beth Israel Deaconess Medical Center. Drs Kalish, Assmann and Kruskall have successful collaborative relationships from prior transfusion-related research projects.